Modular jetting devices

ABSTRACT

A jetting device and/or fluid module includes a nozzle with a fluid outlet, a body including a fluid chamber and a fluid inlet in fluid communication with the fluid chamber, and a valve seat disposed in the fluid chamber, where the valve seat includes an opening in fluid communication with the fluid outlet. The jetting device also includes a movable element having a top portion and a bottom portion, where the top portion is disposed external to the fluid chamber and arranged to be contacted by a reciprocating drive pin, and where the bottom portion is disposed within the fluid chamber. Finally, the jetting device also includes a sealing member contacting the movable element between the top portion and the bottom portion, where the sealing member also contacts the body, and defines a portion of a boundary of the fluid chamber to seal the fluid chamber.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.13/219,064, filed Aug. 26, 2011, and published as U.S. Patent App. Pub.No. 2013/0048759, on Feb. 28, 2013. This application is also related toU.S. patent application Ser. No. 13/219,070, filed Aug. 26, 2011, andpublished as U.S. Patent App. Pub. No. 2013/0052359, on Feb. 28, 2013,which is hereby incorporated by reference herein in its entirety.

BACKGROUND

The invention relates generally to the application of fluid materialsand, in particular, to devices for use in jetting fluid materials.

Jetting devices may require different types of dispensing valves, ordispensing valve components, that are dedicated to different types ofdispensing applications in electronic industry applications in whichminute amounts of a fluid material is applied onto a substrate. A“jetting device” is a device which ejects, or “jets”, a droplet ofmaterial from the dispenser to land on a substrate, wherein the dropletdisengages from the dispenser nozzle before making contact with thesubstrate. Thus, in a jetting type dispenser, the droplet dispensed is“in-flight” between the dispenser and the substrate, and not in contactwith either the dispenser or the substrate, for at least a part of thedistance between the dispenser in the substrate. Numerous applicationsexist for jetting devices that dispense underfill materials,encapsulation materials, surface mount adhesives, solder pastes,conductive adhesives, and solder mask materials, fluxes, and thermalcompounds. As the type of application for the jetting device changes,the type of jetting device must also adapt to match the applicationchange.

One type of jetting device includes a needle with a tip configured toselectively engage a valve seat. During a jetting operation, the needleof the jetting device is moved relative to the valve seat by a drivingmechanism. Contact between the tip of the needle and the valve seatseals off a discharge passage from a fluid chamber supplied with fluidmaterial under pressure. Thus, to dispense droplets of the fluidmaterial, the valve element is retracted from contact with the valveseat to allow a finite amount of the fluid material to flow through thenewly formed gap and into the discharge passage. The tip of the needleis then moved rapidly toward the valve seat to close the gap, whichgenerates pressure that accelerates the finite amount of fluid materialthrough the discharge passage and causes a droplet of the material to beejected, or jetted, from an outlet of the discharge passage.

Jetting devices are configured for controlled movements above thesubstrate and the fluid material is jetted to land on an intendedapplication area of a substrate. By rapidly jetting the material “on thefly” (i.e., while the jetting device is in motion), the dispenseddroplets may be joined to form a continuous line. Jetting devices maytherefore be easily programmed to dispense a desired pattern of fluidmaterial. This versatility has made jetting devices suitable for a widevariety of applications in the electronics industry. For example,underfill material can be applied using a jetting device to dispensefluid material proximate to one or more edges of the chip, with thematerial then flowing under the chip by capillary action.

In conventional jetting devices, the needle tip that contacts the valveseat is exposed to the jetted fluid material. Consequently, the needlemust include various seals that provide fluid isolation of the drivingmechanism for the needle from the fluid chamber in which the needle tipis located, while permitting the tip of the needle to contact the valveseat to cause fluid material jetting. Seals promote wear and friction,while the needle requires significant travel to develop enough velocityfor the impact with the valve seat that generates the energy necessaryfor the droplet of fluid material to be jetted.

From time to time, it is necessary to clean the internal surfaces ofjetting devices that are wetted with the fluid material being jetted.Because these internal surfaces are difficult to access with cleaningtools, conventional jetting devices also take a significant amount oftime to clean. Disassembling and reassembling the components ofconventional jetting devices is a difficult process that involvesnumerous tools. As a result of the complexity of jetting devices,disassembly and reassembly are lengthy procedures, even for techniciansthat are highly skilled.

While conventional jetting devices have proven adequate for theirintended purpose, improved jetting devices are needed that address theneed for less downtime in maintaining jetting devices, while introducingadditional degrees of flexibility to enable the jetting devices to berelatively easily configured for a variety of jetting applications.

SUMMARY OF THE INVENTION

Subheadings are provided in the summary below to help guide the readerthrough some of the various embodiments of the invention.

Fluid Supply Modules

In one embodiment, a modular jetting device includes a fluid modulehaving a fluid chamber, a fluid inlet to the fluid chamber, a fluidconnection interface to connect the fluid inlet to an external supply ofliquid material, a fluid outlet from the fluid chamber, and a valve seatpositioned between the fluid inlet and the fluid outlet. The modularjetting device further includes a drive module configured toreciprocally move at least a portion of a valve element relative to thevalve seat. The fluid interface permits different fluid supply modulesto supply fluid to the fluid module. A first fluid supply module, whichis connectable to the fluid connection interface, can be configured touse pressurized air to direct the fluid material to the fluid inlet ofthe fluid module. A second fluid supply module, which is alternativelyconnectable to the fluid connection interface, can include a positivedisplacement pump configured to pump the fluid material to the fluidinlet of the fluid module. Either the first supply module or the secondfluid supply module, or another type of fluid supply module, isconnected to the fluid connection interface.

Positive Displacement Pumps

A positive displacement pump may be used in certain embodiments of theinvention. It may include a first piston pump and a second piston pumpconfigured to supply the fluid material in a timed sequence to the fluidinlet of the fluid chamber. A first check valve may be positioned in afirst flow path between the fluid inlet to the fluid chamber and thefirst piston pump. The first check valve can include a spring-loadedmovable body that controls reverse flow from the fluid chamber to thefirst piston pump. A second check valve may be positioned in a secondflow path between the fluid inlet to the fluid chamber and the secondpiston pump. The second check valve can include a spring-loaded movablebody that controls reverse flow from the fluid chamber to the secondpiston pump.

A second set of check valves similar to the first and second checkvalves may be included in the positive displacement pump to controlreverse flow between the first and second piston pumps and a fluidsupply, such as a fluid-filled syringe. Specifically, a third checkvalve may be positioned in the first flow path between the fluid supplyand the first piston pump. The first check valve may include aspring-loaded movable body that controls reverse flow of the fluidmaterial from the first piston pump to the fluid supply. A fourth checkvalve may be positioned in the second flow path between the secondpiston pump and the fluid supply. The fourth check valve may include aspring-loaded movable body that controls reverse flow of the fluidmaterial from second piston pump to the fluid supply. The third checkvalve in this second set opens and closes in conjunction with the firstcheck valve and the fourth check valve in this second set opens andcloses in conjunction with the second check valve to permit amounts offluid material to be alternatingly pumped from the fluid supply to thefluid module by the first and second piston pumps.

Each of the piston pumps of the modular jetting device may include apiston cylinder, a piston disposed inside the piston cylinder, amotorized carriage configured to move the piston relative to the pistoncylinder to intake the fluid material into the piston cylinder and todischarge the fluid material from the piston cylinder, and a gripperconnected to the carriage to releasably connect the carriage with thepiston of each pump. The grippers can be released from the pistons topermit the pumps to be easily removed.

The fluid module of the modular jetting device may include a fluidpassageway coupling the fluid inlet with the fluid chamber. The modularjetting device may further include a diaphragm in communication with thefluid passageway and a load sensor coupled with the diaphragm. Thediaphragm is configured to receive or sense a pressure from the fluidmaterial flowing in the fluid passageway from the fluid inlet to thefluid chamber. The pressure received by the diaphragm is transferred asa force to a load sensor.

In one preferred embodiment where the positive displacement pump isused, a syringe that supplies the fluid is connected to a first checkvalve to the positive displacement pump which is connected by a secondcheck valve to the fluid chamber.

Fluid Module Actuated by External Drive Pin

In another embodiment, a fluid module is provided for a jetting devicehaving a drive pin external to the fluid module that is reciprocated byan actuator. The fluid module includes a nozzle with a fluid outlet, amodule body, a valve seat, a movable element, and a valve element. Themodule body includes a first portion with a fluid inlet, a secondportion configured to support the nozzle, and a fluid chamber. Anopening of the valve seat communicates with the fluid outlet and a partof the movable element defines a boundary of the fluid chamber. Thevalve element may be enclosed within the fluid chamber and is attachedto the movable element. Alternatively, the valve element and movableelement may comprise a single element. The valve element is moved towardthe valve seat by contact between the drive pin and the movable element.

The fluid module may further include a biasing element contacting themovable element and configured to apply an axial spring force to themovable element. The valve element and movable element are capable ofmoving away from the valve seat after contact by the drive pin and underthe action of the axial spring force.

The first portion of the module body may include a fluid passagewaycoupling the fluid inlet with the fluid chamber. The fluid module mayfurther include a diaphragm in communication with the fluid passageway.The diaphragm is configured to receive a pressure from a fluid materialflowing in the fluid passageway from the fluid inlet to the fluidchamber and to transfer the pressure as a force to a load sensor.

In an alternative embodiment, the position of upper stop for the movableelement and the spacing of the nozzle seat below the valve can beadjusted.

Coupling Mechanism for Fluid Module

In yet another embodiment, a modular jetting device includes an actuatorbody, a drive module extending from the actuator body, a fluid module,and a heat transfer member disposed at least partially about the fluidmodule. The fluid module has a fluid chamber, a fluid inlet to the fluidchamber, a valve element, a nozzle with a fluid outlet from the fluidchamber, and a valve seat positioned between the valve element and thenozzle. The fluid module is supported by the actuator body. The valveelement is separate from the drive module and is configured to bereciprocally moved by the drive module relative to the valve seat. Themodular jetting device further includes a coupling mechanism having atleast one arm that couples the heat transfer member and the fluid moduleto the actuator body. The at least one arm is configured to bevertically moved between first and second positions. In the firstposition, the at least one arm couples the heat transfer member and thefluid module to the actuator body. In the second position, the at leastone arm provides a non-contacting relationship between the heat transfermember and fluid module, and the actuator body, so that the heattransfer member and fluid module can be decoupled from the at least onearm and the actuator body.

The coupling mechanism of the modular jetting device may, for example,further include a manually actuatable lever connected to the at leastone arm. The lever may be moved to move the at least one arm between thefirst and second positions. As another alternative, a threaded knobfixed to a threaded member that is threadably connected to the at leastone arm can be rotated to move the at least one arm between the firstand second positions.

The fluid chamber of the modular jetting device may have a wall which isconfigured to be reciprocally moved by the drive module. Thereciprocating movement of the wall causes the valve element toreciprocally move relative to the valve seat.

Fluid Module Useable with Different Drive Modules

In yet another embodiment, a modular jetting device includes a fluidmodule including a fluid chamber, a fluid inlet to the fluid chamber, afluid outlet, and a valve seat positioned between the fluid inlet andthe fluid outlet, as well as a valve element that is reciprocallymovable relative to the valve seat. The modular jetting device furtherincludes a first drive module that can be utilized to cause movement ofthe valve element and a second drive module that can alternatively beutilized to cause movement of the valve element. The second drive moduleis configured to operate by a different motive force than the firstdrive module, and the modular jetting device can be configured usingeither the first drive module or the second drive module.

The first drive module of the modular jetting device may be apiezoelectric drive module and the second drive module of the modularjetting device may be an electro-pneumatic drive module.

Controller

In another embodiment, a modular jetting device includes a fluid modulehaving a fluid chamber configured to contain a fluid material, a fluidinlet to the fluid chamber, a fluid outlet from the fluid chamber, and avalve seat positioned between the fluid inlet and the fluid outlet. Themodular jetting device further includes a drive module configured toreciprocally move at least a portion of a valve element relative to thevalve seat between an open position in which the portion of the valveelement is retracted from the valve seat to permit the fluid material tobe discharged from the fluid outlet and a closed position in which thevalve element engages the valve seat to halt the flow of the fluidmaterial from the fluid outlet. The modular jetting device furtherincludes a fluid supply module connected to a fluid connectioninterface. The fluid supply module includes a positive displacement pumpconfigured to pump fluid material to the inlet of the fluid chamber. Acontroller transmits a start time signal to the positive displacementpump indicating a start time for the positive displacement pump to pumpfluid material to the inlet of the fluid chamber and a pumping flow ratesignal used to compare actual flow rate to a desired flow rate and tomake flow rate corrections. The controller concurrently transmits astart time signal to the drive module to move the valve element to theopen position at a predetermined first delay period after the start timesignal to start a dispensing operation and then repeatedly moving thevalve element between the opened and closed positions during thedispensing operation and at a predetermined cycle rate that iscorrelated with the flow rate. The controller transmits an end timesignal to the positive displacement pump to stop pumping fluid materialto the inlet of the fluid chamber. The controller concurrently transmitsan end time signal to the drive module causing the valve element toremain in the closed position at a predetermined second delay periodafter the end time to stop the dispensing operation.

The modular jetting device may further include a load sensor configuredto measure pressure and communicate the pressure as the signals to thecontroller. The load sensor is coupled to a diaphragm that is incommunication with a fluid passageway of the fluid module coupling thefluid inlet with the fluid chamber. The diaphragm is configured toreceive a force from a fluid material flowing in the fluid passagewayfrom the fluid inlet to the fluid chamber and to transfer the force tothe load sensor.

The positive displacement pump may include first and second piston pumpsconfigured to supply the fluid material in a timed sequence to the fluidinlet of the fluid chamber. The controller may be configured to respondto signals from the load sensor to control transitions between the firstpiston pump and the second piston pump.

Some Advantages of Modularity

The design architecture of the jetting devices of the variousembodiments of the invention reduces maintenance downtime and improvesflexibility and usability of a jetting device. Specifically, differentcomponent modules can be assembled based on application requirements.The modular design includes a wetted path segregated from the mechanicaldrive, which allows different mechanical drivers such as piezoelectricdrive module, a pneumatic drive module, or an electromagnetic drivemodule to be used as different options. Thus, a drive module that isappropriate for the application and target sale price of the particularjetting device product model to the user can be selected. The modulardesign can also accommodate different fluid supply modules, again tooptimize the jetting device for the application and target sale price tothe user.

Due to the modularity provided the assembled components of the jettingdevice, the mechanical drive module for the jetting device includes nowetted parts. In other words, the fluid material that is dispensed bythe jetting device is segregated and isolated from the drive module forthe jetting device. The fluid module includes the wetted path for thedispensed fluid material but is constructed to separate the fluidmaterial from the mechanical drive module. As a consequence, the jettingdevice is easier to assemble, disassemble, clean, and maintain.Components of the jetting device are readily interchangeable, which alsosimplifies assembly, cleaning, and maintenance and reduces downtime ofthe jetting device.

These improvements to conventional jetting devices limit the amount offluid material in the wetted path and eliminate the slidingseal/friction/wear of a fluid seal, while enabling the strikingmechanism to accelerate faster because the striking mechanism is outsideof the fluid path and is therefore not influenced by fluid resistance tomotion or the resistance of a fluid seal. The invention permits onefluid module to be easily interchange with a fluid module havingdifferent characteristics such as a different sized valve element andvalve seat and/or a different size discharge orifice for the nozzle topromote optimal droplet size and separation from the nozzle during ajetting operation.

In that the pump can be easily removed, as noted above, this comprises asecond wetted component, in addition to the fluid module, that can beeasily removed for cleaning or maintenance, or replacement with a likeor different fluid module.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of theinvention and, together with a general description of embodiments of theinvention given above, and the detailed description given below, serveto explain the principles of the embodiments of the invention.

FIG. 1 is a perspective view of a modular jetting device in accordancewith an embodiment of the invention.

FIG. 1A is a perspective view similar to FIG. 1 in which an outerhousing of the modular jetting device has been removed for purposes ofdescription.

FIG. 2 is a cross-sectional view taken generally along line 2-2 in FIG.1A.

FIG. 2A is a view of a portion of the piezoelectric drive module.

FIG. 2B shows an alternative embodiment of the modular jetting device.

FIG. 2C shows an alternative embodiment of the modular jetting device.

FIG. 3 is an enlarged cross-sectional view of a portion of FIG. 2.

FIG. 3A shows an alternative embodiment.

FIG. 4 is a perspective view of a modular jetting device in accordancewith an alternative embodiment of the invention.

FIG. 4A is a perspective view similar to FIG. 4 in which an outerhousing of the modular jetting device has been removed for purposes ofdescription.

FIG. 5 is a cross-sectional view taken generally along line 5-5 in FIG.4 and showing a first piston pump of the positive displacement pumpduring an intake cycle.

FIG. 5A is a cross-sectional view similar to FIG. 5 in which the checkvalves associated with the first piston pump of the positivedisplacement pump are repositioned during a discharge cycle.

FIG. 5B is a cross-sectional view taken generally along line 5B-5B inFIG. 4 and showing a second piston pump of the positive displacementpump during an intake cycle.

FIG. 5C is a cross-sectional view similar to FIG. 5B in which the checkvalves associated with the second piston pump of the positivedisplacement pump are repositioned during a discharge cycle.

FIG. 6 is a cross-sectional view taken generally along line 6-6 in FIG.4A.

FIG. 7 is a perspective view similar to FIG. 4A, but with componentsremoved for purposes of illustration, that illustrates the releasemechanism for the fluid module.

FIG. 8A is a view in partial cross section taken generally along line8A-8A in FIG. 7.

FIG. 8B is a view similar to FIG. 8A in which the lever of the releasemechanism has been actuated to a position in which the fluid module islowered relative to the actuator body.

FIG. 8C shows an alternative embodiment.

FIG. 9A is a view in cross section similar to FIG. 8A taken generallyalong line 9A-9A in FIG. 7.

FIG. 9B is a view similar to FIG. 9A in which the lever of the releasemechanism has been actuated to a position in which the fluid module islowered relative to the actuator body.

FIG. 10A is a view in partial cross section taken generally along line10A-10A in FIG. 8A.

FIG. 10B is a view similar to FIG. 10A and taken generally along line10B-10B in FIG. 8B.

FIG. 11A is a view in cross section taken generally along line 11A-11Ain FIG. 8A.

FIG. 11B is a view similar to FIG. 11A and taken generally along line11B-11B in FIG. 8B.

FIG. 12A is a view in cross section taken generally along line 12A-12Ain FIG. 8A.

FIG. 12B is a view similar to FIG. 12A and taken generally along line12B-12B in FIG. 8B.

FIG. 13 is a perspective view of a modular jetting device in accordancewith an alternate embodiment of the invention.

FIG. 13A is a perspective view similar to FIG. 13 in which an outerhousing of the modular jetting device has been removed for purposes ofdescription.

FIG. 14 is a diagrammatic cross-sectional view taken generally alongline 14-14 in FIG. 13A showing only the fluid module, heater and drivemodule.

DETAILED DESCRIPTION

Subheadings are provided in some sections below to help guide the readerthrough some of the various embodiments, features and components of theinvention.

Generally, the embodiments of the invention are primarily directed to adispensing valve in the form of a modular jetting device that is modularin a number of respects. One aspect is that the valve internal to thefluid module of the modular jetting device can be actuated by either apneumatic drive module, an electromagnetic drive module, or apiezoelectric drive module. Another aspect is that fluid material can besupplied to the fluid chamber of the fluid module of the modular jettingdevice from fluid supply modules comprising either a pressurized syringeor positive displacement pump. Another aspect is that the modularjetting device includes a fluid module that seals all the wetted partsfrom the valve drive module. By the use of this design, the valve drivemodules do not penetrate the fluid module, but rather engages a wall, orportion, of the fluid chamber module to reciprocate a valve elementdisposed within the fluid module. This enables fluid modules to beeasily removed for cleaning or service, or interchanged with differentfluid modules for different applications. For example, a fluid modulebest suited for the application of the dispensing of solder flux jettingcan be used for that application, and a different fluid module bestsuited for the application of the dispensing of adhesive in an underfillapplication can be used for the different requirements of thatapplication. In addition, a quick release coupling mechanism is providedthat enables the fluid module to be quickly released from the modularjetting device for cleaning or service or to be interchanged with adifferent fluid module. In addition, spring biased grippers enable thepump to be easily removed as will be explained in more detail below.

With reference to FIGS. 1, 1A, 2, and 3 and in accordance with anembodiment of the invention, a dispensing valve in the representativeembodiment of a modular jetting device 10 includes a fluid module 12having a fluid connection interface 20, a valve element 14, apiezoelectric drive module 16, a movable needle or drive pin 36 coupledwith the piezoelectric drive module 16, and an outer cover 18 housingthe piezoelectric drive module 16. The outer cover 18 is composed ofthin sheet metal and is fastened to the actuator body of the modularjetting device 10 by conventional fasteners. The primary supportstructure of the modular jetting device 10 is provided by a lower member115, an upper member 113 and a support wall 111 that joins the upper andlower members 113, 115.

The modular jetting device 10 is supplied with pressurized fluidmaterial from a syringe 22, which is supported by a syringe holder 26mounted as an appendage to the outer cover 18. Generally, the fluidmaterial in the syringe 22 may be any material or substance known by aperson having ordinary skill in the art to be amenable to jetting andmay include, but is not limited to, solder flux, solder paste,adhesives, solder mask, thermal compounds, oil, encapsulants, pottingcompounds, inks and silicones. The syringe 22 operates as a fluid supplymodule for the modular jetting device 10.

The modular jetting device 10 may be installed in a machine or system(not shown) for intermittently jetting amounts of a fluid material ontoa substrate and may be moved relative to the substrate as the amounts offluid material are jetted. The modular jetting device 10 may be operatedsuch that a succession of jetted amounts of the fluid material aredeposited on the substrate as a line of spaced-apart material dots. Thesubstrate targeted by the modular jetting device 10 may support varioussurface mounted electronic components, which necessitates non-contactjetting of the minute amounts of fluid material rapidly and withaccurate placement to deposit fluid material at targeted locations onthe substrate. As detailed hereinbelow, the fluid module 12 isaccessible for easy removal without tools from the bottom of the modularjetting device 10.

The Fluid Module

As best visible in FIG. 3, the fluid module 12 includes a nozzle 28, amodule body 30, and a fluid chamber 38 in communication with the fluidconnection interface 20. A first section or portion 40 of the modulebody 30 includes a fluid inlet 42 and a passageway 47, 47 a that couplesthe fluid inlet 42 in fluid communication with the fluid chamber 38. Afluid conduit 44 (FIGS. 1, 1A) extends from the syringe 22 to the fluidinlet 42 for placing the fluid module 12 in fluid communication with thefluid material contained inside the syringe 22 and for supplying thefluid material under pressure from the syringe 22 to the fluidconnection interface 20. In this embodiment, the fluid conduit 44 istypically a length of tubing directly connecting the outlet of thesyringe 22 with the fluid connection interface 20 without anyintervening structure. In one embodiment, the fluid connection interface20 includes a Luer fitting.

The syringe 22 may be configured to use pressurized air to direct thefluid material to flow toward the fluid inlet 42 and ultimately to thefluid chamber 38 of the fluid module 12. The pressure of the pressurizedair, which is supplied to the head space above the fluid materialcontained in the syringe 22, may range from five (5) psig to sixty (60)psig. Typically, a wiper or plunger (not shown) is disposed between theair pressure in the head space and the fluid material level inside thesyringe 22, and a sealing cap (not shown) is secured to the open end ofthe syringe barrel for supplying the air pressure.

A second portion 45 of the module body 30 is configured to support thenozzle 28. A centering piece 46 aligns a fluid outlet 48 in the nozzle28 with a passageway 50 extending through the second portion 45 of themodule body 30. A valve seat 52 is disposed between the fluid inlet 42and the fluid outlet 48. The valve seat 52 has an opening 56 in fluidcommunication with the fluid outlet 48. The centering piece 46 maintainsthe fluid outlet 48 in nozzle 28, the passageway 50 in the secondportion 45 of module body 30, and the opening 56 in valve seat 52 in aconcentric alignment. These pieces 45, 46, 52 and 28 can be held inplace in place by an adhesive bond between the components.Alternatively, some or all of the elements 45, 46, 52 and 28 could bemade as a single unified piece. FIG. 2B shows an embodiment where all ofthe elements 45, 46, and 52 are made as a single unified piece 400, andnozzle 402 is attached to the unified piece 400 by, for example,adhesive or by a threaded connection.

The fluid module 12 further includes a strike plate in the form of awall 62 of a movable element 60. A biasing element 68, whichperipherally contacts the movable element 60, is configured to apply anaxial spring force to the movable element 60.

A sealing ring 64 supplies a sealing engagement between an insert 63 andthe exterior of the movable element 60. The part of the moveable element60 which is below sealing ring, or O-ring, 64 defines a part of theboundary of the fluid chamber 38. The valve element 14 is attached tomoveable element 60 and is located inside the fluid chamber 38 at alocation between the wall 62 of the movable element 60 and the valveseat 52. Alternatively, the element 14 and movable element 16, includingstrike plate 62, may be made as a single unified piece, as shown in FIG.2C.

A third portion 32 of the module body may be attached to the top ofinsert 63 by a friction fit. The second portion 45 of the module body isattached by a friction fit to the first portion 40 of the module body toenclose all the other components of the fluid module. Namely, once firstportion 40 and second portion 45 are pressed together they enclose theseparts of the fluid module: nozzle 28, valve seat 52, centering piece 46,valve element 14, movable element 60, sealing ring 64, biasing element68, insert 63 and third portion 32 of the module body. Thus, in thepreferred embodiment, the fluid module is comprised of elements 45, 40,28, 52, 46, 14, 60, 64, 68, 63 and 32.

While certain of the components of the fluid module have been describedas being connected by friction fit, the friction fits between thesecomponents could be replaced by threads to permit the components to bedisassembled and reassembled.

In the assembled position described above and shown in FIG. 3, thepassageways 47 and 47 a that couple the fluid inlet 42 in fluidcommunication with the fluid chamber 38 are provided as follows. Annularpassageway 47 a is created by a space provided between first portion 40and third portion 32 of module body 30. Passageway 47 is provided bygrooves or channels formed on the outside of insert 63. When insert 63is press fit into second portion 45 of the module body 30, the grooveson the exterior of insert 63 and the interior surface of second portionform passageways 47. In embodiments where the insert 33 is threadablyconnected to portion 45, a hole could be drilled through insert 33 toprovide a flow passage between fluid inlet 42 and fluid chamber 38.

In an alternative embodiment of the fluid module shown in FIG. 3A, thirdportion 32 is threaded into insert 63 by means of threads 32 a. Thisthreaded engagement permits the position of the lower surface 32 b, ofthird portion 32, which is the upper stop for movable element 60, to beadjusted. The greater the distance the surface 32 b is positioned abovebiasing element 68, the greater the stroke of the valve 14. In addition,this embodiment permits the position of valve seat 350 to be adjusted.Valve seat 350 and nozzle 352 are retained in a retainer cup 354 whichis threaded at threads 356 into the second portion 45. The furtherretainer cup 354 is threaded up into second portion 45, the closer thevalve seat 350 is positioned relative to the valve element 14. A locknut 358 is provided to fix the position of valve seat 350 relative tovalve element 14 once the retainer cup 354 has been threaded the desireddistance into second portion 45.

Actuation of the Fluid Module by an External Drive Pin

The drive pin 36 projects through a bore 66 in the third portion 32 ofthe fluid module body 30. The tip 34 of the drive pin 36 is locatedadjacent to the wall 62 of the movable element 60 and on an oppositeside of the wall 62 from the valve element 14.

While the valve element 14 is exposed to the fluid material containedinside the fluid chamber 38, the bore 66 containing the drive pin 36 isisolated from the fluid material in fluid chamber 38 so that the drivepin 36 is not wetted by the fluid material. As a result, theconstruction of the modular jetting device 10 can omit the conventionalfluid seals that permit powered motion of the drive pin 36 whileisolating the driving or actuation mechanism (e.g., piezoelectric drivemodule 16) for the drive pin 36 from the fluid material in the fluidchamber 38.

The drive pin 36 is indirectly coupled with the valve element 14 andoperates as a component of the piezoelectric drive module 16 or otherdrive module. The drive pin 36 and valve element 14 jointly cooperate todispense fluid material by jetting from the modular jetting device 10.When the drive pin 36 is moved to cause the valve element 14 to contactthe valve seat 52, the tip 34 of the drive pin 36 operates much like theoperation of a hammer to by striking the wall 62 of the movable element60 to transfer its force and momentum to the wall 62, which in turncauses the valve element 14 to rapidly strike the valve seat 52 and jeta droplet of material from the jetting device. Specifically, the valveelement 14, which is not directly connected with the drive pin 36, isconfigured to be moved into contact with the valve seat 52 by an impulseimparted by the tip 34 of the actuated drive pin 36 to the wall 62 ofthe movable element 60. As a result, the drive pin 36 is actuated and anamount fluid material is jetted from the fluid chamber 38 without anyportion of the drive pin 36, including but not limited to the tip 34,being wetted by the jetted fluid material. When contact between thedrive pin 36 and wall 62 is removed, the axial spring force applied bythe biasing element 68 acts to move the valve element 14 and movableelement 60 away from the valve seat 52 in a direction aligned with thelongitudinal axis of the drive pin 36. Each reciprocating cycle of thedrive pin 36 and valve element 14 jets a droplet of the fluid material.The cycle is repeated to jet sequential droplets of fluid material asrequired.

The surface of the valve element 14 facing the valve seat 52 may have acurvature to match the shape of the surface of the valve seat 52encircling opening 54. As a result of the shape matching, a fluid sealis temporarily formed when the valve element 14 has a contactingrelationship with valve seat 52 during jetting. Establishment of thefluid seal during motion of the valve element 14 halts the flow of fluidmaterial from the fluid chamber 38 past the valve seat 52.

In embodiments where a unified movable element 300, shown in FIG. 2C, isused, the drive pin 34 would contact the upper portion 302 of element300 to cause the lower end 304 to contact the valve seat and jet adroplet of material. As indicated in FIG. 2C, in the same way as in thepreviously disclosed embodiment, the outer surface of element 300 wouldbe sealed against O-ring 64 and the spring 68 would provide an upwardbiasing force on the element 300.

The Heater

A heater 76, which has a body 80 that operates as a heat transfermember, at least partially surrounds the fluid module 12. The heater 76may include a conventional heating element (not shown), such as acartridge-style resistance heating element residing in a bore defined inthe body 80. The heater 76 may also be equipped with a conventionaltemperature sensor (not shown), such as a resistive thermal device(RTD), a thermistor, or a thermocouple, providing a feedback signal foruse by a temperature controller in regulating the power supplied to theheater 76. The heater 76 includes pins 79 that contact respective soft,electrically conductive contacts 59 associated with the guide block 74 b(later described) in order to provide signal paths for a temperaturesensor and to provide current paths for transferring electrical power tothe heating element and temperature sensor. As will be explained in moredetail below, the fluid module 12 sits within the heater 76, and whenthe heater 76 is drawn against the actuator body 74 by retainer arms(later described) the fluid module is held in compression between theheater 76 and actuator body 74.

Piezoelectric Drive Module

With reference to FIGS. 1A, 2, and 2A, in one embodiment, thepiezoelectric drive module 16 is used to actuate the valve 14 of fluidmodule 12. Piezoelectric drivers for dispensing valves are known. Forexample, U.S. Pat. No. 5,720,417 shows a piezoelectric driver used toactuate the valve of a fluid dispenser and is incorporated by referenceherein in its entirety for all purposes. In the present embodiment, thepiezoelectric drive module 16 includes piezoelectric stacks 92 a and 92b, a plunger 93, an asymmetrical flexure 94. Flexure 94 is an integralpart of actuator body 74 and includes a coupling element 97 thatconnects the flexure 94 to the plunger 93. A spring 96 applies a springforce to the plunger 93 and piezoelectric stacks 92 a, 92 b to keep themin compression. As best shown in FIGS. 1A and 4A, the actuator body 74is sandwiched between guide blocks 74 a and 74 b, which will bedescribed later in more detail. The guide blocks 74 a and 74 b areattached to actuator body 74 by conventional fasteners. Thepiezoelectric stacks 92 a, 92 b, the plunger 93, and the spring 96 areconfined as an assembly between mechanical constraints supplied by a Cshaped bracket 55 having upper and lower extensions 56, 58. Bracket 55,shown in phantom is FIG. 1A, is supported between load cell pad 115 a,which is attached to lower member 115, and a support member 111 a thatis attached to upper member 113.

The plunger 93 functions as a mechanical interface connecting thepiezoelectric stack 92 with the asymmetrical flexure 94. The spring 96is compressed in the assembly such that the spring force generated bythe spring 96 applies a constant load on piezoelectric stack 92, whichpreloads the piezoelectric stack 92. The asymmetrical flexure 94, whichmay be comprised of a metal, has an arm 95 that is physically securedwith an end of the drive pin 36 opposite to the tip 34 of drive pin 36.The asymmetrical flexure 94 functions as a mechanical amplifier thatconverts the relatively small displacement of the piezoelectric stack 92into a useful displacement for the drive pin 36 that is significantlylarger than the displacement of the piezoelectric stack 92.

The piezoelectric stack 92 of piezoelectric drive module 16 is alaminate comprised of layers of a piezoelectric ceramic that alternatewith layers of a conductor as is conventional in the art. The springforce from spring 96 maintains the laminated layers of the piezoelectricstack 92 in a steady state of compression. The conductors in thepiezoelectric stack 92 are electrically coupled with a driver circuit98, which supplies current-limited output signals, in a manner wellknown in the art, with pulse width modulation, frequency modulation, ora combination thereof. When power is periodically supplied from thedriver circuit 98, electric fields are established that change thedimensions of the piezoelectric ceramic layers in the piezoelectricstack 92.

The dimensional changes experienced by the piezoelectric stack 92, whichare mechanically amplified by the asymmetrical flexure 94, move thedrive pin 36 linearly in a direction parallel to its longitudinal axis.When the piezoelectric ceramic layers of the piezoelectric stack 92expand, the spring 96 is compressed by the force of the expansion andthe asymmetrical flexure 94 pivots about a fixed pivot axis to causemovement of the tip 34 of drive pin 36 upward in FIG. 2 away from thewall 62 of movable element 60. This allows biasing element 68 to movethe valve element 14 away from valve seat 52. When the actuation forceis removed and the piezoelectric ceramic layers of the piezoelectricstack 92 are permitted to contract, the spring 96 expands and theasymmetrical flexure 94 pivots to move the drive pin 36 downward in FIG.2 so that the tip 34 moves into contact with the wall 62, causing thevalve element 14 to contact valve seat 52 and jet a droplet of material.Thus, in the de-energized state, the piezo stack assembly maintains thevalve in a normally closed position. In normal operation, theasymmetrical flexure 94 intermittently rocks in opposite directionsabout a fixed pivot axis as the stack 92 a, 92 b is energized andde-energized to move the tip 34 of drive pin 36 into and out of contactwith the wall 62 of the movable element 60 to jet droplets of materialat a rapid rate.

The driver circuit 98 for piezoelectric drive module 16 is controlled bya controller 99. The controller 99 may comprise any electrical controlapparatus configured to control one or more variables based upon one ormore inputs. The controller 99 can be implemented using at least oneprocessor 170 selected from microprocessors, micro-controllers,microcomputers, digital signal processors, central processing units,field programmable gate arrays, programmable logic devices, statemachines, logic circuits, analog circuits, digital circuits, and/or anyother devices that manipulate signals (analog and/or digital) based onoperational instructions that are stored in a memory 172. The memory 172may be a single memory device or a plurality of memory devices includingbut not limited to random access memory (RAM), volatile memory,non-volatile memory, static random access memory (SRAM), dynamic randomaccess memory (DRAM), flash memory, cache memory, and/or any otherdevice capable of storing digital information. The controller 99 has amass storage device 174 that may include one or more hard disk drives,floppy or other removable disk drives, direct access storage devices(DASD), optical drives (e.g., a CD drive, a DVD drive, etc.), and/ortape drives, among others.

The processor 170 of the controller 99 operates under the control of anoperating system 175, and executes or otherwise relies upon computerprogram code embodied in various computer software applications,components, programs, objects, modules, data structures, etc. Theprogram code 176 residing in memory 172 and stored in the mass storagedevice 174 also includes control algorithms that, when executing on theprocessor 170, control the operation of the piezoelectric drive module16 and, in particular, provide control signals to the driver circuit 98for driving the piezoelectric drive module 16. The computer program codetypically comprises one or more instructions that are resident atvarious times in memory 172, and that, when read and executed by theprocessor 170, causes the controller 99 to perform the steps necessaryto execute steps or elements embodying the various embodiments andaspects of the invention.

Various program code described herein may be identified based upon theapplication within which it is implemented in a specific embodiment ofthe invention. However, it should be appreciated that any particularprogram nomenclature that follows is used merely for convenience, andthus the invention should not be limited to use solely in any specificapplication identified and/or implied by such nomenclature. Furthermore,given the typically endless number of manners in which computer programsmay be organized into routines, procedures, methods, modules, objects,and the like, as well as the various manners in which programfunctionality may be allocated among various software layers that areresident within a typical computer (e.g., operating systems, libraries,API's, applications, applets, etc.), it should be appreciated that theinvention is not limited to the specific organization and allocation ofprogram functionality described herein.

The controller 99 may include a human machine interface (HMI) that isoperatively connected to the processor 170 in a conventional manner. TheHMI (not shown) may include output devices, such as alphanumericdisplays, a touch screen, and other visual indicators, and input devicesand controls, such as an alphanumeric keyboard, a pointing device,keypads, pushbuttons, control knobs, etc., capable of accepting commandsor input from an operator and communicating the entered input to theprocessor 170, and of displaying information to the operator.

The controller 99 may optionally be used to control the operation ofdevices supporting the operation of a manufacturing tool that embodiesthe modular jetting device 10 of the embodiments of the invention. Forexample, the controller 99 is coupled with a load cell 166 thatgenerates pressure measurement readings through its connection withdiaphragm 162 by means of rod 164, as described below. These pressuremeasurement readings are communicated to the controller 99 as feedbackfor use in controlling the operation of the modular jetting device 10when the positive displacement pump 102 is deployed.

Positive Displacement Pump

With reference to FIGS. 4, 4A, 5, 5A-C, and 6 in which like referencenumerals refer to like features in FIGS. 1-3 and in accordance with analternative embodiment of the invention, the modular jetting device 10may include a supply module 100 connectable to the fluid connectioninterface 20 at a location between the syringe 22 and the fluidconnection interface 20. The supply module 100 includes a positivedisplacement pump 102, a manifold block 103, and a plurality of checkvalves 104, 106, 108, 110 in the fluid paths inside the manifold block103. The positive displacement pump 102, which is illustrated as areciprocating-type positive displacement pump, can be mounted to thelower member 115 by conventional fasteners.

The positive displacement pump 102 is configured to pump the fluidmaterial to the inlet to the fluid chamber 38 of the fluid module 12. Tothat end, the positive displacement pump 102 includes a first pistonpump 112 and a second piston pump 114 configured to be controlled in acoordinated manner to supply the fluid material in a timed sequence tothe fluid connection interface 20 of the fluid module 12. The controller99 executes program code that provides the sequence timing andcoordinates the operation of the first and second piston pumps 112, 114.

The first piston pump 112 has a piston cylinder 116, a piston 118disposed inside the piston cylinder 116, and a carriage 120. One end ofthe piston 118 includes a head 119 and a set of grippers or jaws 122.Jaws 122 are pivotally attached to the carriage 120 and grip the head119 in a releasable clamping action. Each of the jaws 122 has arespective hook 121 that, when the jaws 122 are closed to clamp the head119, engages a side edge of the head 119. The jaws 122, which are springbiased to a closed position by, for example, torsion springs, may beopened by the application of a manual force that overcomes the springbias and separates the jaws 122. When the manual force is removed, thejaws 122 close to clamp the head 119 of the piston 118. Alternatively, afixed stop (not shown) may be mounted to support element 115 c. Supportelement 115 c contacts the top of pump 102 and is rigidly attached tosupport wall 111. The fixed stop may open the jaws 122 to disengage thepiston head 119 as the jaws 122 are moved into contact with it.

The carriage 120 associated with piston 118 rides on a linear bearing126 as a linear motion constraint and is moved linearly relative to thelinear bearing 126 by a lead screw 128. Linear bearing 126 is attachedat its bottom end to support element 115 c and at its upper end to uppermember 113. The rotary motion of lead screw 128 is driven by a motor 130and is converted by the motion of the carriage 120 into linear motion ofthe piston 118 inside piston cylinder 116. The motor 130 can bebi-directionally driven by instructions from the controller 99 so thatthe lead screw 128 is rotated in both rotational senses and the piston118 can be moved in opposite linear directions relative to the pistoncylinder 116 by the rotation of the lead screw 128.

A detector in the representative form of a rotary encoder 131 tracks themotion of the motor 130 and thereby permits the controller 99 to trackthe location of the carriage 120 along the length of the lead screw 128.The number of motor encoder counts detected by the rotary encoder 131and supplied (e.g., as optical or electrical signals) from the rotaryencoder 131 to the controller 99 effectively tracks the displacement ofthe piston 118 and can be correlated with the amount of fluid materialbeing displaced. The controller 99 may use the signals from the rotaryencoder 131 for closed-loop feedback control of the operation of thepositive displacement pump 102 and, in particular, control of theoperation of the first piston pump 112.

The second piston pump 114, which may be constructed identically to thefirst piston pump 112, includes a piston cylinder 132, a piston 134, anda carriage 136. One end of the piston 134 includes a head 141 and a setof grippers or jaws 138, which are pivotally attached to the carriage136, grips the head 119 in a releasable clamping action. Each of thejaws 138 has a respective hook 143 that, when the jaws 138 are closed toclamp the head 141, engages a side edge of the head 141. The jaws 138,which are spring biased to a closed position by, for example, torsionsprings, may be opened by the application of a manual force thatovercomes the spring bias and separates the jaws 138. When the manualforce is removed, the jaws 138 close to clamp the head 141 on the piston134. Again, a fixed stop may alternately be used to open the jaw 138upon contact.

The carriage 136 associated with piston 134 rides on a linear bearing140 as a linear motion constraint and is moved linearly relative to thelinear bearing 140 by a lead screw 142. Linear bearing 140 is attachedat its lower end to support element 115 c and at its upper end to uppermember 113. The rotary motion of lead screw 142 is driven by a motor 144and is converted by the motion of the carriage 136 into linear motion ofthe piston 134 inside piston cylinder 132. The motor 144 can bebi-directionally driven by instructions from the controller 99 so thatthe lead screw 142 is rotated in both rotational senses and the piston134 can be moved in opposite linear directions relative to the pistoncylinder 132 by the rotation of the lead screw 142.

A rotary encoder 145 tracks the motion of the motor 144 of the secondpiston pump 114 and thereby permits the controller 99 to track thelocation of the carriage 136 along the length of the lead screw 142. Thenumber of motor encoder counts detected by the rotary encoder 145 andsupplied (e.g., as optical or electrical signals) to the controller 99effectively tracks the displacement of the piston 134 and can becorrelated with the amount of fluid material being displaced. Thecontroller 99 may use the signals from the rotary encoder 145 forclosed-loop feedback control over the operation of the positivedisplacement pump 102 and, in particular, control over the operation ofthe second piston pump 114.

The Manifold Block

The piston pumps 112, 114 operate in conjunction with the manifold block103, which may be composed of aluminum. Pumps 112, 114 are attached tomanifold block 103 by conventional fasteners (not shown). As best shownin FIGS. 5, 5A-C, and 6, disposed inside the manifold block 103 are afeed passageway 150, a discharge passageway 152, a first branchpassageway 154, and a second branch passageway 156. The dischargepassageway 152 is coupled in fluid communication with the fluidconnection interface 20. The first branch passageway 154 couples thefeed passageway 150 in fluid communication with the discharge passageway152. The second branch passageway 156 couples the feed passageway 150 influid communication with the discharge passageway 152. Passageways 150,152, 154 constitute a first fluid path coupled with the first pistonpump 112. Passageways 150, 152, 156 constitute a second fluid pathcoupled with the second piston pump 114.

The interior volume of the piston cylinder 116 of the first piston pump112 fluidly communicates with the first branch passageway 154. Checkvalves 104, 106 (FIGS. 5, 5A) are positioned on opposite sides of thecentrally-located fluid connection between the piston cylinder 116 andthe first branch passageway 154.

As best shown in FIGS. 5, 5A, and 6, check valve 104 is disposed in thefluid path between the syringe 22 and the fluid connection with thepiston cylinder 116 of the first piston pump 112. The check valve 104 isspecifically positioned at the transition from the one of the outlets ofthe feed passageway 150 to an inlet of the first branch passageway 154.The check valve 104 includes a spring-loaded movable body 182 that canbe displaced from a seat 183 by forward flow so that fluid material canbe transferred from the syringe 22 to the first piston pump 112 and fillthe piston cylinder 116 with fluid material during an intake cycle offirst piston pump 112 as shown in FIG. 5. During a discharge cycle offirst piston pump 112 as shown in FIG. 5A, the orientation of the checkvalve 104 prohibits reverse flow of fluid material from the first pistonpump 112 to the syringe 22. Specifically, the spring-loaded movable body182 of the check valve 104 will be seated against seat 183 by the fluidpressure in first branch passageway 154, which is generated by themotion of the piston 118 inside the piston cylinder 116 during thedischarge cycle.

Check valve 106 is disposed in the fluid path between the fluid inlet 42to the fluid chamber 38 and the fluid connection with the pistoncylinder 116 of the first piston pump 112, and is also thereforedisposed in the fluid path between the fluid connection interface 20 andthe first piston pump 112. The check valve 106 is specificallypositioned at the transition from one of the inlets to the dischargepassageway 152 and an outlet from the first branch passageway 154. Thecheck valve 106 includes a spring-loaded movable body 184 that can bedisplaced from a seat 185 by forward flow so that fluid material can bepumped by the first piston pump 112 to the fluid chamber 38 during adischarge cycle as shown in FIG. 5A. During an intake cycle of firstpiston pump 112 as shown in FIG. 5, the orientation of the check valve106 prohibits reverse flow of fluid material from the fluid chamber 38to the first piston pump 112. Specifically, the spring-loaded movablebody 184 of the check valve 106 will be seated against seat 185 by thefluid pressure in first branch passageway 154, which is generated by themotion of the piston 118 inside the piston cylinder 116 during theintake cycle.

The piston 118 is moved within the piston cylinder 116 by the motion ofcarriage 120, which is powered by motor 130, in a direction 190 tointake fluid material from the feed passageway 150, as depicted in FIG.5. In response to the motion of piston 118, the check valve 104 opensand fluid material flows, as diagrammatically shown by reference numeral192, past the opened check valve 104 through the first branch passageway154 from the feed passageway 150 into the interior of the pistoncylinder 116. The fluid material fills the space in the piston cylinder116 vacated by the piston 118. The potential source of the reverse flowof fluid material from fluid chamber 38, which is prevented by checkvalve 106, occurs when the piston cylinder 116 is being filled by fluidmaterial and suction is applied on the outlet side of the first pistonpump 112.

When the piston cylinder 116 contains an appropriate amount of fluidmaterial and at the end of the stroke, the motor 130 reverses the motionof the carriage 120. The reverse motion of the carriage 120 causes thepiston 118 to move in a direction 191, as depicted in FIG. 5A. Motion ofthe piston 118 relative to the piston cylinder 116 expels the fluidmaterial in the piston cylinder 116, as diagrammatically shown byreference numeral 193, under pressure toward the fluid connectioninterface 20. Check valve 106 opens to permit the fluid material to flowthrough first branch passageway 154 to discharge passageway 152. Checkvalve 104 closes to prohibit reverse fluid flow from the piston cylinder116 to the syringe 22.

The interior volume of the piston cylinder 132 of the second piston pump114 communicates with the second branch passageway 156 at a locationbetween the outlet from the feed passageway 150 and the inlet to thedischarge passageway 152. Check valves 108, 110 (FIGS. 5B, 5C) arelocated in the second branch passageway 156.

As best shown in FIGS. 5B, 5C, 6, check valve 108 is disposed in thefluid path between the syringe 22 and the fluid connection with thepiston cylinder 132 of the second piston pump 114. The check valve 108is specifically positioned at the transition from the one of the outletsof the feed passageway 150 to an inlet of the second branch passageway156. The check valve 108 includes a spring-loaded movable body 186 thatcan be displaced from a seat 187 by forward flow so that fluid materialcan be transferred from the syringe 22 to the second piston pump 114 andfill the piston cylinder 132 with fluid material during an intake cycleof second piston pump 114 as shown in FIG. 5B. During a discharge cycleof second piston pump 114 as shown in FIG. 5C, the orientation of thecheck valve 108 prohibits reverse flow of fluid material from the secondpiston pump 114 to the syringe 22. Specifically, the spring-loadedmovable body 186 of the check valve 108 will be seated against seat 187by the fluid pressure in the second branch passageway 156, which isgenerated by the motion of the piston 134 inside the piston cylinder 132during the discharge cycle.

Check valve 110 is disposed in the fluid path between the fluid inlet 42to the fluid chamber 38 and the fluid connection with the pistoncylinder 132 of the second piston pump 114, and is also thereforedisposed in the fluid path between the fluid connection interface 20 andthe second piston pump 114. The check valve 110 is specificallypositioned at the transition from one of the inlets to the dischargepassageway 152 and an outlet from the second branch passageway 156, andis also therefore disposed in the fluid path between the fluidconnection interface 20 and the second piston pump 114. The check valve110 includes a spring-loaded movable body 188 that can be displaced froma seat 189 by forward flow so that fluid material can be pumped by thesecond piston pump 114 to the fluid chamber 38 during a discharge cycleas shown in FIG. 5C. During an intake cycle of second piston pump 114 asshown in FIG. 5B, the orientation of the check valve 110 prohibitsreverse flow of fluid material from the fluid chamber 38 to the secondpiston pump 114. Specifically, the spring-loaded movable body 188 of thecheck valve 110 will be seated against seat 189 by the fluid pressure inthe second branch passageway 156, which is generated by the motion ofthe piston 134 inside the piston cylinder 132 during the intake cycle.

The piston 134 is moved within the piston cylinder 132 by the motion ofcarriage 136, which is powered by the motor 144, in a direction 194 in adirection to intake fluid material from the feed passageway 150, asdepicted in FIG. 5B. In response to the motion of piston 134, the checkvalve 108 opens and fluid material flows, as diagrammatically indicatedby reference numeral 196, past the opened check valve 108 through thesecond branch passageway 156 from the feed passageway 150 into theinterior of the piston cylinder 132. The fluid material fills the spacein the piston cylinder 132 vacated by the piston 134. The potentialsource of the reverse flow of fluid material from fluid chamber 38,which is prevented by check valve 110, occurs when the piston cylinder132 is being filled with fluid material and suction is applied on theoutlet side of the second piston pump 114.

When the piston cylinder 132 contains an appropriate amount of fluidmaterial and at the end of the stroke, the motor 144 reverses the motionof the carriage 136. The reverse motion of the carriage 136 causes thepiston 134 to move in a direction 195, as depicted in FIG. 5C. Motion ofthe piston 134 relative to the piston cylinder 132 expels the fluidmaterial in the piston cylinder 132, as diagrammatically indicated byreference numeral 197, under pressure toward the fluid connectioninterface 20. Check valve 110 opens to permit the fluid material to flowthrough second branch passageway 156 to discharge passageway 152. Checkvalve 108 closes to prohibit reverse fluid flow of fluid material fromthe piston cylinder 132 to the syringe 22.

Control of Pump Wink

The alternation between the first piston pump 112 of positivedisplacement pump 102 and the second piston pump 114 of positivedisplacement pump 102 switches the source of fluid material supplied tothe discharge passageway 152 and fluid inlet 42. In other words, thepiston pumps 112, 114 alternate in operation between intake anddischarge cycles. Unless precautions are taken, a “wink”, or reduction,of fluid pressure and fluid flow can occur at the changeover betweenintake and discharge cycles when the positive displacement pump 102switches from piston pump 112 to piston pump 114 and when the positivedisplacement pump 102 switches from piston pump 114 to piston pump 112.The intake and discharge cycles are both servo operations conducted bythe controller 99 and are effectively independent of each other. Thecontroller 99 is only used to coordinate the operation of the pistonspumps 112, 114 during the transition between intake and dischargecycles. The pressure sensor, which is comprised of diaphragm 162, rod164, and load cell 166, assesses the fluid pressure at a location in theflow path that is downstream from the positive displacement pump 102 andupstream of the fluid chamber 38.

A condition that indicates a wink is about to occur is when one of thepiston pumps 112, 114 is loaded with fluid material at acylinder-is-full point near the end of an intake cycle and the other ofthe piston pumps 112, 114 is nearly emptied of fluid material at atime-to-refill point near the end of a discharge cycle. Thetime-to-refill point is represented by an encoder count-based addressfrom rotary encoder 131 that represents that the piston 118 hasdischarged a targeted amount of fluid material from the piston cylinder116 or alternatively from rotary encoder 145 that represents that thepiston 134 has discharged a targeted amount of fluid material from thepiston cylinder 132. Conversely, the cylinder-is-full point is aposition for the piston 118, as reflected by an encoder count-basedaddress from rotary encoder 131, that indicates the maximum amount offluid material is contained in the piston cylinder 116 or a position forthe piston 134, as reflected by an encoder count-based address fromrotary encoder 145, that indicates the maximum amount of fluid materialis contained in the piston cylinder 132. Each of the piston pumps 112,114 includes high and low optical limit switches that may optionally beused to indicate the time-to-refill or cylinder-is-full indications.

Once the controller 99 discerns the approach of a transition between thepiston pumps 112, 114 and while monitoring the output of the pressuresensor, the controller 99 will cause the full one of the piston pumps112, 114 to begin driving fluid out of its cylinder to the fluid module12, and simultaneously will reverse the other of the piston pumps 112,114 so that it stops driving fluid out of its cylinder to the fluidmodule 12 and starts refilling its cylinder instead. The pressure sensormay perceive and measure an increase in fluid pressure or a decrease influid pressure during the transition, which the controller 99 will sensefrom the signals communicated by the pressure sensor. In response to thefluid pressure increase or decrease during the transition, thecontroller 99 may provide speed corrections to the motors 130, 144 inorder to maintain constant pressure and constant flow. A program codeexecuting on the controller 99 may calculate the needed speedcorrections and adjust the operation of the motors 130, 144 to providethe speed corrections.

The Pressure Sensor

Having described the function of the pressure sensor, details of itsconstruction will now be described. With reference to FIGS. 1A, 2, 5,and 6, the fluid inlet 42 and passageway 47 connecting the fluidconnection interface 20 with the fluid chamber 38 include a number ofinterconnected segments of various lengths and orientations. Shortlyafter the fluid material passes through the fluid connection interface20, the fluid material flowing in fluid inlet 42 interacts with adiaphragm 162. The diaphragm 162 includes a peripheral ring that issecurely anchored and a thin, semi-rigid membrane surrounded about itsperimeter by the peripheral ring. The front side of the membrane of thediaphragm 162 is wetted by the flowing fluid material in the fluid inlet42 and the back side of the membrane of the diaphragm 162 is not wetted.The differential fluid pressure across the opposite sides of themembrane of diaphragm 162 causes the membrane to deflect in proportionto the amount of fluid pressure applied by the fluid material to thediaphragm 162. Increasing fluid pressures in fluid inlet 42 causegreater amounts of deflection.

A rod 164 extends from the backside of the membrane of diaphragm 162 tocontact load cell 166. The deformation of the membrane of the diaphragm162 varies in proportion to the fluid pressure. As the fluid pressurechanges, the diaphragm 162 communicates a force to the load cell 166 viathe intervening rod 164 that is proportional to the fluid pressure. Theload cell 166 communicates the pressure measurement readings to thecontroller 99 for the modular jetting device 10. In this manner, thediaphragm 162 and load cell 166 cooperate to operate as a pressuresensor that measures and assesses fluid pressure in the fluid inlet 42for use in controlling the operation of the modular jetting device 10.

Removal of Supply Module

The jaws 122, 138 permit the supply module 100, comprised of pump 102and manifold block 103, to be easily disconnected from the fluidconnection interface 20 between the syringe 22 and the fluid connectioninterface 20 and from the jetting device 10 for cleaning or maintenance.To remove supply module 100, the carriages 120, 136 are driven down totheir lowest point on FIG. 4A to push out any fluid in the cylinders116, 132. At their lowest point, the jaws can be automatically opened byfixed stops as described above, or manually opened, to disengage thepiston heads 119, 141. Next, the internally threaded fluid couplings 26a, 20 a (see FIG. 5B) are disengaged from the syringe 22 and fluidconnection interface 20, respectively. Finally, the conventionalfasteners (not shown), such as bolts, that connect pump 102 to lowermember 115 are removed so that the supply module 100, comprised of pump102 and manifold block 103, can be removed as a unit for replacementwith a like supply module 100, or for maintenance and cleaning of itswetted surfaces. Thus, not only is the fluid module 12 easy todisconnect from the jetting device 10 for maintenance, cleaning andreplacement, but in addition the supply module 100 is also easy todisconnect from the jetting device 10 for maintenance, cleaning andreplacement. Since the fluid module and the supply module include allthe wetted surfaces of the jetting device 10, it is highly advantageousto be able to quickly remove and replace both of these components.

In addition, when the supply module 100 is disconnected, the syringe 22can be directly connected in fluid communication with the fluidconnection interface 20 using the fluid conduit 44 so that either of twofluid supply modules can be used to provide liquid material to the fluidmodule 12. Thus, the syringe 22 may be directly connected with the fluidconnection interface 20 to define one fluid supply module (FIGS. 1-3) ofthe modular jetting device 10. Likewise, the supply module 100 (FIGS.4-7) of the modular jetting device 10, which includes the syringe 22,may be connected with the fluid connection interface 20 to defineanother fluid supply module.

Coordination of the Piston Pump with the Drive Modules

The operation of the piston pumps 112, 114 may be coordinated to movethe pistons 118, 134 within the respective piston cylinders 116, 132such that the stream of fluid material supplied through the fluidconnection interface 20 to the fluid module 12 can be substantiallycontinuous and uninterrupted and at a flow rate that is substantiallythe same as the rate at which a liquid material is being jetted from thefluid module 12. The controller 99 may receive a pumping flow ratesignal from the encoders 131, 145 indicating the flow rate at which thepositive displacement pump 102 is pumping material into the fluid inlet42 and ultimately into the fluid chamber 38.

In use, the controller 99 sends a start time signal to the positivedisplacement pump 102 indicating a start time for the positivedisplacement pump 102 to pump fluid material to the fluid inlet 42 ofthe fluid chamber 38 and a desired pumping flow rate signalrepresentative of the rate at which material is to be jetted from fluidmodule 12. Using the encoders, the actual pumping rate can be comparedto the desired pumping rate to make flow rate corrections. When thecontroller 99 sends a start time signal to the positive displacementpump 102, the controller 99 concurrently transmits a start time signalto the piezoelectric piezoelectric drive module 16, or pneumatic drivemodule 202 shown in the FIG. 14 embodiment (later described), to movethe valve element 14 to the open position at a predetermined first delayperiod after the start time signal to start the positive displacementpump 102. Controller 99 then repeatedly moves the valve element 14between the opened and closed positions during the jetting operation ata predetermined cycle rate that is correlated with the flow rate. Thecontroller 99 also utilizes data indicating the volume of material to bejetted through the fluid module 12 during the current jetting operationand once that amount of material has been jetted, as determined from theencoders 131, 145, controller 99 sends an end time signal to thepositive displacement pump 102 to stop pumping fluid material to thefluid inlet 42 of the fluid chamber 38. The controller 99 concurrentlytransmits an end time signal to the piezoelectric drive module 16, orpneumatic drive module 202, causing the valve element 14 to remain inthe closed position at a predetermined second delay period after the endtime to stop the jetting operation.

One advantage of supplying a jetting valve with fluid from a positivedisplacement pump is better “shot to shot” accuracy. This means that,for example, the same size dot can be jetted consistently, regardless ofchanges in parameters such as viscosity (caused by temperature changes)of the material being jetted, or fluid pressure of the material beingjetted. The reason is that positive displacement pumping ensures thatall material being supplied to the fluid module is jetted out of thefluid module. Thus, assuming a constant flow rate of material into thefluid module and a constant jetting frequency in dots per minute, thesize of each droplet, or dot, of material jetted out of the fluid moduleshould be the same. By contrast, in the case of a jetting valve suppliedfrom a syringe, for example, if the pressure in the syringe increases,larger dots will be jetted, and if the pressure in the syringe drops,smaller dots will be jetted. Likewise, if the temperature of thematerial in the syringe drops causing the material's viscosity toincrease, the dots being jetted will become smaller, and if thetemperature of the material in the syringe increases causing thematerial's viscosity to be reduced, the dots being jetted will becomelarger. These variations in jetted dot, or droplet, size are reducedwith the positive displacement pump embodiment of this invention.

Release Mechanism for Fluid Module and Heater

With reference to FIGS. 7, 8A, B, 9A, B, 10A, B, 11A, B and 12A, B,which show only the components of the jetting device 10 that areinvolved with the release mechanism, the fluid module 12 and heater 76of the modular jetting device 10 are configured with a release mechanism72 that facilitates rapid attachment and removal of the heater 76 andfluid module 12 without disturbing other components of the modularjetting device 10 and without the necessity of using tools to loosen andtighten conventional fasteners. The heater 76 and fluid module 12 aremovable between a raised first position (FIGS. 8A, 9A, 10A, 11A, 12A) inwhich the fluid module 12 is operatively coupled with the modularjetting device 10 and a lowered second position (FIGS. 8B, 9B, 10B, 11B,12B) in which the fluid module 12 is removable from the modular jettingdevice 10.

With initial reference to FIGS. 7, 8A,B, 9A,B, 10A,B, 11A,B and 12A,B,the release mechanism may include a lever 86 having a cam 84 and a rod87 that couples the cam 84 with a draw bar 81. The lever 86 is pivotallysupported on the upper member 113 of the actuator body of the modularjetting device 10. The cam 84 is a smoothly curved surface that contactsa curved seat 85 and that rides on the curved seat 85 as the lever 86 ismanually pivoted about pivot pin 248 between first and second positions.The rod 87 has a threaded end that is centrally coupled with the pivotpin 248 and another threaded end coupled with the draw bar 81. The cam84 and curved seat 85 cooperate to convert rotational movement of thelever 86 into linear motion of the rod 87. The pivot pin 248 is offsetlaterally relative to a geometrical center of the cam 84. As the lever86 is manually rotated about pivot pin 248 from the first position(FIGS. 7, 8A, 9A, and 10A) toward a second position (FIGS. 7, 8B, 9B,and 10B) as indicated by the single-headed arrow 53 visible on FIGS. 7,8A and the cam 84 rides across the curved seat 85, the rod 87 movesdownward as indicated by the single headed arrow visible on FIGS. 7, 8A,9A, 10A.

When the lever 86 is manually rotated about pivot pin 248 from thesecond position toward the first position in the opposite rotationalsense to single headed arrow 53, the rod 87 moves upward in an oppositelinear direction to arrow 51. The rod 87 passes through a clearanceopening 65 in the lower member 115. A spring 69, which is compressedbetween the draw bar 81 and the lower member 115, provides a spring biasthat assists in forcing the draw bar 81 to move downward as the lever 86is rotated about the pivot pin 248 toward the second position.

L-shaped arms 88, 90 are pivotally connected by respective pivot pins 73to the lower member 115 and are disposed along opposite side faces ofthe lower member 115. The L-shaped arms 88, 90 are similar inconstruction. Each of the L-shaped arms 88, 90 has a respective armsegment 89 a, 89 b that projects away from the respective pivot pointwith the lower member 115. The draw bar 81 is disposed between the armsegments 89 a, 89 b, which extend in a parallel fashion adjacent to theopposite side faces of the draw bar 81. Each of the arm segments 89 a,89 b includes a C-shaped finger 101 that is secured with a portion ofthe draw bar 81. As the draw bar 81 moves relative to the lower member115, the motion of the draw bar 81 pivots the arms 88, 90 in the samerotational sense about pivot axes defined each respective pivot pins 73.

The L-shaped arm 88 has an arm segment 91 a that is joined with armsegment 89 a and the L-shaped arm 90 has an arm segment 91 b that isjoined with arm segment 89 b. The arm segments 91 a, 91 b project in aparallel fashion transversely to arm segments 89 a, 89 b and are spacedapart so that the assembly of the heater 76 and the fluid module 12 cangenerally fit between the arms 88, 90. As best shown in FIGS. 11A and11B, arm segment 91 a passes through a slot 74 c in guide member 74 aand arm segment 91 b passes though a slot 74 d in guide member 74 b.When the lever 86 is pivoted toward the second position, the draw bar 81moves away from the lower member 115 and each of the arms 88, 90 pivotsabout its respective pivot pin 73 so that the arm segments 91 a, 91 bare downwardly displaced, as indicated by the single-headed arrows 61(FIG. 7). Because the arm segments 91 a, 91 b are attached to the heater76, as will be later described, and because the fluid module 12 sits ontop of the heater 76 as previously described, the downward displacementof the arms 88, 90 lowers the fluid module 12 and heater 76 down andaway from the actuator body 74. In particular, a gap, G, is formedbetween the actuator body 74 and the assembly comprised of the fluidmodule 12 and heater 76.

As best shown in FIGS. 11A, B and 12A, B, the end of arm 88 is notchedwith a notch 70 that is slightly spaced from the tip of arm segment 91a. Similarly, the end of arm 90 is notched with a notch 71 that isslightly spaced from the tip of arm segment 91 b. The heater 76 includesslots 82, 83 that are defined in the body 80 and spring-loaded latches77, 78 inside the slots 82, 83. The latches 77, 78 are secured to thebody 80 by respective pivot pins 178, 180 that define pivot axes. Thelatches 77, 78 cooperate with the notches 70, 71 in the arm segments 91a, 91 b of arms 88, 90 to secure heater 76 to the arms 88, 90. After thefluid module 12 and heater 76 are lowered away from the actuator body 74to create the gap, G, the latches 77, 78 in cooperation with the notches70, 71 continue to secure the heater 76, and the fluid module 12 sittingon top of the heater 76, to the remainder of the modular jetting device10. The lowering of the assembly is an initiate stage of removing thefluid module 12 and heater 76.

Compression spring 148 spring biases the latch 77 outwardly from theslot 82 and into engagement with the notch 70 in the arm segment 91 a ofarm 88. Latch 77 is forcibly engaged with the notch 70 in arm 88 by thespring bias applied by compression spring 148 and an opposite force ofgreater magnitude than the spring bias must be manually applied todisengage the latch 77 from the notch 70. Compression spring 146 springbiases the latch 78 outwardly from the slot 83 and into engagement withthe arms 88, 90. Latch 78 is forcibly engaged with the notch 71 in thearm segment 91 b of arm 90 by the spring bias applied by compressionspring 146 and an opposite force of greater magnitude than the springbias must be manually applied to disengage the latch 78 from the notch71. The physical contact between the latch 77 and arm 88 and thephysical contact between the latch 78 and arm 90 collectively block therelease of the assembly of fluid module 12 and heater 76 after theinitial lowering by pivoting motion of the L-shaped arms 88, 90.

Once the assembly is lowered away from the actuator body 74, the fluidmodule 12 and heater 76 are removed from the modular jetting device 10by performing additional manual actions. In the representativeembodiment, an inward manual force, diagrammatically indicated by thesingle-headed arrows 67 (FIG. 12A), can be applied to the latches 77, 78in a pinching or squeezing motion by the fingers of the operator's handto release the latches 77, 78 from the notches 70, 71. Each of thelatches 77, 78 includes a slot and a pin guided by the slot so that thelatches 77, 78 move in an arc when the inward manual force is applied.The force applied by each of the compression springs 146, 148 opposesthe inward manual force such that the lowered assembly is retainedunless the inward manual force exceeds the spring biasing of the latches77, 78 by the compression springs 146, 148. When the latches 77, 78 aremanually released by this pinching motion as shown in FIGS. 11B, 12B,the obstruction is removed and the fluid module 12 and heater 76 arefreed for further downward manual movement relative to the arms 88, 90and can be manually removed as an assembly from the arms 88, 90. Afterthe fluid module 12 and heater 76 are removed, the fluid module 12,which has a slip fit, or slight interference fit, within the centralbore of the heater body 80, can be pushed out of the body 80 of heater76 to be cleaned or replaced with an identical fluid module, or adifferent fluid module for a different jetting application.

To install the fluid module 12 after cleaning, the removal process isreversed. Specifically, the cleaned fluid module 12 is pushed into thebody 80 of heater 76. The assembly of the heater 76 and the fluid module12 is moved upwardly toward the piezoelectric drive module 16 and overthe arms 88, 90. While pressing the latches 77, 78 so that the latches77, 78 do not obstruct vertical movement of the assembly relative to thearms 88, 90, the assembly of the heater 76 and the fluid module 12 israised until the heater 76 contacts the actuator body 74. The latches77, 78 are released and the engagement between the latches 77, 78 andnotches 70, 71 is verified by applying a modest downward force on theheater 76. The lever 86 is rotated to a closed position to clamp thefluid module into compressive contact with the actuator body 74.Specifically, the reverse motion of the lever 86 from the secondposition to the first position raises the draw bar 81, which pivots thearms 88, 90 in an opposite rotational sense to raise the heater 76 andfluid module 12 and clamp it into contact with the actuator body 74.Note that in this clamped position, the ends of the arms 89 a, 89 b thatare opposite to pivot pins 73 deflect downwardly, like springs, to holdthe heater 76 and fluid module 12 snugly into contact with the actuatorbody 74. In the clamped position, spring-loaded pins 79 on the heater 76contact the respective soft, electrically conductive contacts 59 inguide block 74 b, as best shown in FIG. 9A.

In an optional embodiment, as shown in FIG. 8C, once the lever 86 hasbeen rotated to the first position to clamp the fluid module 12 intocontact with the actuator body, a positive lock feature can be activatedto hold the lever 86 in the first position. For example, a spring biascatch member 400 could be slidably received within a chamber 402 in thelever 86. The member 400 includes a catch 404 on its lower side andwould be biased to the left in FIG. 8C by a spring 406. As the lever 86is rotated into the first position, the rounded lower surface of catch404 would cause it to move to the right in FIG. 8C and compress thespring 406 until it passes through the opening 410 provided in the uppersurface of upper member 113. After catch 404 passes through opening 410,the spring moves catch 404 to the left in FIG. 8C to engage the tab 408that projects from the upper member 113. This structure automaticallylocks the lever 86 in the first position. To release the lever from thefirst position, the member 400 would be manually pushed to the right inFIG. 8C to compress spring 406 and move catch 404 to the right so thatit can pass through the opening 410 in upper member 113. The lever 86can then be moved to the second position shown by phantom lines in FIG.8C to release fluid module 12.

Electro-Pneumatic Drive Module

With reference to FIGS. 13, 13A, and 14 in which like reference numeralsrefer to like features in FIGS. 1-12 and in accordance with analternative embodiment, a modular jetting device 200 includes anelectro-pneumatic drive module 202 that is configured to operate by atype of different motive force than the piezoelectric drive module 16. Amotive force is a force that produces or causes movement in a direction.In this instance, the movement produced or caused by the motive force isreciprocating and the moved objects are the drive pin 36, the valveelement 14, and/or the movable element 60. The motive force of theelectro-pneumatic drive module 202 is air pressure acting on a pneumaticpiston 204 and the motive force of the piezoelectric drive module 16 isdimensional changes occurring in a piezoelectric stack 92. Depending onthe model of the jetting device 10, either the piezoelectric drivemodule 16 or the electro-pneumatic drive module 202 is incorporated inthe jetting device 10 with the fluid module 12. In either case, thedesign of the fluid module 12 is the same. Thus, the fluid module 12 iseasily usable with either drive module.

The electro-pneumatic drive module 202 includes the pneumatic piston204, a pair of air chambers 216, 218 separated from each other by thepneumatic piston 204, a first solenoid valve 206, and a second solenoidvalve 210. The pneumatic piston 204 is physically connected with one endof the drive pin 236. The pneumatic piston 204 is movable as a functionof the pressurization of the air chambers 216, 218 and, as a result, thevolumes of the air chambers 216, 218 are dependent on the position ofthe pneumatic piston 204. The solenoid valves 206, 210 regulate thepressurization of the air chambers 216, 218. The solenoid valves 206,210 may each be any three-way or four-way valve that operates to switcha flow of pressurized air among flow paths as understood by a person ofordinary skill in the art.

The mechanical valve of the first solenoid valve 206 is coupled by afirst passageway 208 penetrating the body 201 of the drive module 202with air chamber 216 on one side of the pneumatic piston 204. Themechanical valve of the first solenoid valve 206 is configured to portair pressure from an air supply 222 through the first passageway 208 tothe air chamber 216 and to exhaust air pressure from the air chamber216. The mechanical valve of the second solenoid valve 210 is coupled bya second passageway 212 penetrating the body of the drive module 202with the air chamber 218 on the opposite side of the pneumatic piston204. The mechanical valve of the second solenoid valve 210 is configuredto port air pressure from the air supply 222 through the secondpassageway 212 to the air chamber 218 and to exhaust air pressure fromthe air chamber 218.

The coils of the solenoid valves 206, 210 are electrically actuated byrespective driver circuits 224, 226 that are operated under thesupervision of the controller 99. The driver circuits 224, 226 are of aknown design with a power switching circuit providing electrical signalsto the solenoid valves 206, 210, respectively. The driver circuits 224,226 may be integrated into the construction of the solenoid valves 206,210. In response to an electrical signal supplied to the coil ofsolenoid valve 206 from the driver circuit 224, the solenoid valve 206switches the flow path in the mechanical valve so that the firstpassageway 208 is coupled with the air supply 222 and pressurized airflows from the air supply 222 into the air chamber 216. When theelectrical signal to the coil of solenoid valve 206 is discontinued, thesolenoid valve 206 switches the flow path in the mechanical valve sothat an exhaust of solenoid valve 206 is coupled with the firstpassageway 208 and the air pressure is exhausted from air chamber 216.Thus, the mechanical valve associated with solenoid valve 206 isnormally set, in the solenoids unpowered state, to vent the chamber 216to atmosphere. Similarly, in response to an electrical signal suppliedto the coil of solenoid valve 210 from the driver circuit 226, thesolenoid valve 210 switches the flow path in the mechanical valve sothat the second passageway 212 is coupled with the air supply 222 andpressurized air flows from the air supply 222 into the air chamber 218.When the electrical signal to the coil of solenoid valve 210 isdiscontinued, the solenoid valve 210 switches the flow path in themechanical valve so that an exhaust of solenoid valve 210 is coupledwith the second passageway 212 and the air pressure is exhausted fromair chamber 218. Thus, the mechanical valve associated with solenoidvalve 210 is likewise normally set, in the solenoids unpowered state, tovent the chamber 218 to atmosphere.

The operation of the solenoid valves 206, 210 may be coordinated to openand close the modular jetting device 200 for jetting fluid material fromfluid module 12. The controller 99 may send one control signal to thedriver circuit 224 for solenoid valve 206 causing air chamber 216 to bepressurized and another independent control signal to the driver circuit226 for solenoid valve 210 causing air chamber 218 to be pressurized.The pressurization of air chamber 218 applies a force to the pneumaticpiston 204, which moves the drive pin 236 away from the wall 62 of themovable element 60. The pressurization of air chamber 216 applies aforce to the pneumatic piston 204, which moves the drive pin 236 towardthe wall 62 of the movable element 60. When either of the controlsignals is absent, the corresponding one of the air chambers 216, 218 iscoupled with ambient pressure as mentioned above.

A compression spring 228 is captured between a spring retainer 229 andthe pneumatic piston 204. The force applied by the compression spring228 to the spring retainer 229 acts on the pneumatic piston 204 anddrive pin 236 in the same direction as the force from the air pressurein air chamber 216 acting on the pneumatic piston 204. As a result, theforce of the compression spring 228 acting on pneumatic piston 204 andthe force from the pressurization of air chamber 216 acting on pneumaticpiston 204 are approximately collinear and in the same direction.Conversely, the force of the compression spring 228 acting on pneumaticpiston 204 and the force from the pressurization of air chamber 218acting on pneumatic piston 204 are approximately collinear and inopposite directions. Normally, since both solenoids 206 and 210 aredeenergized and in that state connect their respective chambers 216, 218to exhaust ports, spring 228 normally the only force acting on piston204 and it pushes down on piston 204 two force drive pin 236 downwardly,which in turn forces the valve element 14 against the valve seat 52 in aclosed position.

To open the valve, air pressure is supplied to chamber 218 below piston204 which raises the piston and thereby raises the drive pin 236 out ofcontact with the wall 62. This causes the internal spring 68 of thefluid module to withdraw the valve element 14 from contact with thevalve seat 52. To close the valve, air pressure is supplied to chamber216 above the piston 204 which acts together with the spring 228 to pushthe piston downwardly to cause the drive pin 236 to contact the wall 62to close valve element 14 against the valve seat and jet a droplet offluid material. By repetitively opening and closing the valve in thisway sequential droplets of material can be jetted. If the air pressurein chamber 218 is vented relatively quickly after air pressure isapplied to chamber 216, then the piston 204 and drive pin 236 will moveat a relatively high speed. If the air pressure in chamber 218 is notvented relatively quickly after air pressure is applied to chamber 216,then the piston 204 and drive pin 236 will move at a slower speed.Generally, it is best to move the drive pin 236 at a relatively fasterspeed when jetting more viscous, or thicker, materials to supply enoughenergy to cause the material to jet as a droplet, and best to move thedrive pin 236 at a relatively slower speed when jetting less viscous,thinner, materials to avoid splashing of the jetted droplets on thesubstrate.

The computer program code in memory 172 and executing on the controller99 can include instructions for operating the solenoid valves 206, 210.The electro-pneumatic drive module 202 may operate at a speed of 300 Hzor higher to jet droplets at 300 Hz or higher from jetting device 10.

Alternative Release Mechanism

The fluid module 12 that is used in conjunction with the modular jettingdevice 200 is identical to the fluid module 12 used in conjunction withmodular jetting device 10 and, therefore, has the interchangeabilitydiscussed above. The fluid module 12 and heater 76 are releasable fromthe electro-pneumatic drive module 202 using an alternate releasemechanism. In this alternate embodiment of the release mechanism, a knob250 replaces lever 86 to moves the arms 288, 290 vertically to releasethe fluid module 12 and heater 76 for removal from the electro-pneumaticdrive module 202.

Arms 288 and 290 include the same slots at their lower ends as arms 89 aand 89 b of the previously described release mechanism embodiment. Sincethe fluid module 12 is identical, the slots cooperate with latches 77,78 in the same way as previously described.

To lower the fluid module 12 and heater 76 in this alternate embodiment,the knob 250 is rotated in a first direction to rotate a threaded screw260 which is fixed to the knob 250. Rotation of the threaded screw 260in this first direction within an internally threaded member 270 that isattached to arms 288 and 290, causes the arms 288 and 290 to movevertically downwardly to space the fluid module 12 and heater 76 fromthe body 201 and form a gap therebetween, that is similar to the gap Gshown in FIG. 9B. The fluid module 12 and heater 76 can now be removedfrom the arms 288 and 290 in the same way as previously described withrespect to arms 89 a and 89 b.

Likewise, the fluid module 12 and heater 76 can be reattached to thearms 288 and 290 in the same way as previously described with respect toarms 89 a and 89 b. Once attached, the knob 250 is rotated in theopposite direction to cause the screw 262 rotate in the oppositedirection within the internally threaded member 270, which in turnraises the arms 288 and 290. Once the fluid module 12 is firmly incontact with the body 201, rotation of the knob 250 is stopped.

References herein to terms such as “vertical”, “horizontal”, “upper”,“lower”, “raise”, “lower”, etc. are made by way of example, and not byway of limitation, to establish a frame of reference. It is understoodby persons of ordinary skill in the art that various other frames ofreference may be equivalently employed for purposes of describing theembodiments of the invention.

It will be understood that when an element is described as being“attached”, “connected”, or “coupled” to or with another element, it canbe directly connected or coupled to the other element or, instead, oneor more intervening elements may be present. In contrast, when anelement is described as being “directly attached”, “directly connected”,or “directly coupled” to another element, there are no interveningelements present. When an element is described as being “indirectlyattached”, “indirectly connected”, or “indirectly coupled” to anotherelement, there is at least one intervening element present.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an”, and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. Furthermore, to the extent that theterms “includes”, “having”, “has”, “with”, “composed of”, or variantsthereof are used in either the detailed description or the claims, suchterms are intended to be inclusive in a manner similar to the open-endedterm “comprising.”

While the present invention has been illustrated by a description ofvarious embodiments and while these embodiments have been described inconsiderable detail, it is not the intention of the applicants torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. For example, in an alternative embodiment, thedrive module used in conjunction with the modular jetting devices 10,200 may be an electromechanical actuator that does not rely on airpressure acting on a pneumatic piston or dimensional changes induced ina piezoelectric stack as a motive force to actuate the drive pin 36.Instead, the electromechanical actuator includes an armature coupledwith the drive pin 36 and an electromagnet that is driven to causemovement of the armature. Thus, the invention in its broader aspects istherefore not limited to the specific details, representative apparatusand method, and illustrative example shown and described. Accordingly,departures may be made from such details without departing from thespirit or scope of applicants' general inventive concept.

What is claimed is:
 1. A jetting device, comprising: a nozzle with afluid outlet; a body including a fluid chamber and a fluid inlet, thefluid inlet in fluid communication with the fluid chamber; a valve seatdisposed in the fluid chamber, the valve seat including an opening incommunication with the fluid outlet; a reciprocating drive pin; an armmechanically coupled to the reciprocating drive pin, the arm being urgedby a spring to bias the reciprocating drive pin downward; a movableelement terminating at a top portion and having a bottom portion, thetop portion being disposed external to the fluid chamber and arranged tobe struck by the reciprocating drive pin, the bottom portion beingdisposed within the fluid chamber and configured to move in a directiontowards the valve seat in response to the top portion being struck bythe drive pin to cause a droplet of fluid from the fluid chamber to bejetted from the fluid outlet; and a sealing member contacting themovable element between the top portion and the bottom portion, and thesealing member defining a portion of a boundary of the fluid chamber toseal the fluid chamber.
 2. The jetting device of claim 1, wherein thebottom portion of the movable element engages the valve seat to causethe droplet of fluid from the fluid chamber to be jetted from the fluidoutlet.
 3. The jetting device of claim 1, wherein a diameter of theopening of the valve seat is greater than a diameter of the fluid outletof the nozzle.
 4. The jetting device of claim 1, wherein the bottomportion of the movable element tapers to a flat surface, the flatsurface engaging with the valve seat.
 5. The jetting device of claim 1,wherein the fluid inlet comprises a fluid passageway having at least aportion that runs in a direction substantially perpendicular to adirection of movement of the bottom portion of the movable elementtoward the valve seat.
 6. The jetting device of claim 1, wherein thefluid inlet connects with the fluid chamber at a direction substantiallyperpendicular to a direction of movement of the bottom portion of themovable element toward the valve seat.
 7. The jetting device of claim 1,wherein the fluid comprises at least one of: solder flux, solder paste,adhesive, solder mask, thermal compound, oil, encapsulant, pottingcompound, ink, or silicone.
 8. The jetting device of claim 1, whereinthe sealing member comprises a sealing ring.
 9. The jetting device ofclaim 1, wherein a longitudinal axis of the drive pin is the same as alongitudinal axis of the movable element.
 10. The jetting device ofclaim 1, wherein the movable element is configured to move away from thevalve seat after the drive pin is reciprocated out of contact with thetop portion of the movable element.
 11. The jetting device of claim 1,wherein the sealing member contacts a periphery of the movable elementbetween the top portion and the bottom portion of the movable element.12. The jetting device of claim 1, wherein an area of contact betweenthe top portion of the movable element and the drive pin is a contiguousflat surface which overlaps with a central longitudinal axis of themovable element.
 13. The jetting device of claim 2, wherein the bottomportion of the movable element strikes the valve seat in response to thetop portion being struck by the drive pin to cause the droplet of fluidfrom the fluid chamber to be jetted from the fluid outlet.
 14. Thejetting device of claim 1, further comprising an actuator mechanicallycoupled to the drive pin, the actuator being configured to causedownward reciprocation of the drive pin.
 15. The jetting device of claim14, wherein the actuator is a piezoelectric actuator.
 16. The jettingdevice of claim 1, wherein the bottom portion of the movable elementengages the valve seat at an inner perimeter of the valve seat.
 17. Thejetting device of claim 1, wherein the fluid chamber is interposedbetween the movable element and the valve seat.
 18. The jetting deviceof claim 1, wherein a surface of the fluid chamber defining the valveseat is perpendicular to the movement direction of the movable elementtowards the valve seat.